• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.2974-2988
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• 2022

Implementation of component isolation in nuclear industry is challenging due to gaps in research and the lack of specific guidelines. In this study, parameters affecting component-level isolation of advanced reactor vessels are identified based on a representative numerical model with explicit consideration of nonlinear soil-structure interaction (SSI). The objective of this study is to evaluate the effectiveness of, and to identify potential limitations of using conventional friction pendulum bearings to seismically isolate vessels. It is found that slender vessels or components are particularly vulnerable to rotational accelerations at the isolation interface, which are caused by rotation of the sub-structure and by excitation of higher modes in the horizontal direction of the seismically isolated system. Component isolation is found to be more effective for relatively stiffer vessels and at sites with stiff soil. Considering that conventional isolators are deficient in resisting axial tension, it is observed that the optimum location for supporting a component to achieve seismic isolation, is at a cross-sectional plane passing through the center of mass of the vessel. These findings are corroborated by numerous simulations of the response of seismically isolated reactor vessels at different nuclear power plant sites subject to a variety of ground motions.

• Journal of Korean Association for Spatial Structures
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• v.8 no.2
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• pp.73-84
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• 2008

The various systems as the seismic resistance systems are used to reduce the seismic response of structure. And the seismic isolation system among them is the system that reduces the seismic vibration to be transmitted from foundation to upper structure. The purpose of isolation system is to lengthen the period of structure and make its period shift from the dominant period of earthquake. In this study, the seismic behavior of arch structure with lead rubber bearing(LRB) and friction pendulum system(FPS) is analyzed. The arch structure is the simplest structure and has the basic dynamic characteristics among large spatial structures. Also, Large spatial structures have large vertical response by horizontal seismic vibration, unlike seismic behavior of normal rahmen structures. When horizontal seismic load is applied to the large spatial structure with isolation systems, the horizontal acceleration response of the large spatial structure is reduced and the vertical seismic response is remarkably reduced.

• Structural Engineering and Mechanics
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• v.75 no.1
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• pp.33-47
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• 2020

In this paper the dynamic behavior of an isolated building subjected to idealized near-fault pulses is investigated. The building is represented with a simple 2-DOF model. Both linear and non-linear behavior of the isolation system is considered. Using dimensional analysis, in conjunction with closed form mathematical idealized pulses, appropriate dimensionless parameters are defined and self-similar curves are plotted on dimensionless graphs, based on which various conclusions are reached. In the linear case, the role of viscous damping is examined in detail and the existence of an optimum value of damping along with its significant variation with the number of half-cycles is shown. In the nonlinear case, where the behavior of the building depends on the amplitude of the excitation, the benefits of dimensional analysis are evident since the influence of the dimensionless 𝚷-terms is easily examined. Special consideration is given to the normalized strength of the non-linear isolation system that appears to play a complex role which greatly affects the response of the 2-DOF. In the last part of the paper, a comparison of the responses to idealized pulses between a linear fixed-base SDOF and the respective isolated 2-DOF with both linear and non-linear damping is conducted and it is shown that, under certain values of the superstructure and isolation system characteristics, the use of an isolation system can amplify both the normalized acceleration and displacement of the superstructure.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.502-505
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• 2004

Now for the first time in Korea pilot project on application of base isolation system to the RC building is carrying out by collaboration with KNHC and DRB dongil. The hybrid-type base isolation system, which is composed of sliding bearings and laminated rubber bearings and can make the resonance period of base isolated buildings comparatively long up to 4 or 5 seconds, is applied to this building. In this paper the overview of this project, the dynamic characteristics of this particular building and the response reduction effect against earthquakes are presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.5
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• pp.131-139
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• 2001

In this paper, aerials gas pipeline vibrations due to the passing of vehicles have been measured, and peak values and characteristics of vibration were analyzed. In order to develop isolation system for gas pipeline, six cases with various support condition and hanging method were tested. The hanger used instead of wore rope isolated almost all vibrations transmitted from main beam. In the results of test, we could decrease response of vibration velocity from 49 % to 56 % and response of vertical vibration acceleration from 49 % to 60 %, because hanger instead of wire rope was used and rubber pads instead of wooden shield plates at support positions for Proofing horizontal vibration were used.

• Computational Structural Engineering
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• v.8 no.1
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• pp.107-113
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• 1995

Spent fuel storage pool should maintain its structural integrity and the safety of stored spent fuels against design earthquake load. In this study, the seismic response analysis of the pool with LRB isolation system is performed for two different earthquakes. To investigate the seismic response of the base isolated pool, the analysis results are compared with the responses of conventional type. In conclusion, the base-isolation system is effective to reduce the seismic forces transmitted to the superstructure and the responses, and to secure the safety of the storage pool and stored spent fuel.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.331-338
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• 2001

Seismic performances of the base isolated model of Five Story Stone Pagoda were studied through shaking table tests. Friction pendulum system (FPS), Pure-friction system with laminated rubber bearing (LRB) and Ball with rubber bearing were selected fur the comparison of performances. Performances of specially designed isolation systems were tested dynamically using shaking table. The test results of isolated model are compared with those of fixed base model. Compared with fixed base model, the isolated model showed that it could withstand much higer intensity of earthquake motion. The Effective Peak Ground Acceleration (EPGA) value of isolated model when the top component tipped over was above twice of that value in case of fixed base model. According to the additional test results, the lower value of coefficient of friction than that of common frictional base isolation systems is more effective to protect the piled multi-block system of Pagoda against moderate intesity of ground motion.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.453-460
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• 2005

In this study, the seismic fragility analysis of a base isolated condensate storage tank installed in the nuclear power plant. The condensate storage tank is safety related structure in a nuclear power plant. The failure of this tank affect significantly to the core damage frequency of the nuclear power plants. The seismic analysis of the liquid storage tank was performed by the simple calculation method and the dynamic time storage analysis method. The convective and impulsive fluid mass is modeled as added masses proposed by several researchers. To evaluate the effectiveness of the isolation system, the comparison of HCLPF and core damage frequencies in non-isolated and isolated cases are carried out. It can be found from the results that the seismic isolation system increases the seismic capacity of a condensate storage tank and decreases the core damage frequency significantly.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.291-298
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• 2000

This paper describes a theoretical and experimental investigation into an active vibration isolation system in which four electromagnetic actuators are installed in parallel with each of four passive mounts placed between a piece of equipment and a vibrating base structure. Decentralised velocity feedback control is employed, where each actuator is operated independently by feeding back the absolute equipment velocity at the same location. Although one end of each actuator acts at the sensor positions on the equipment, the control system is not collocated because of the reactive forces acting on the flexible base structure, whose dynamics are strongly coupled with the mounted equipment. Isolation of low frequency vibration is considered where the equipment can be modelled as a rigid body and the mounts as lumped parameter springs and dampers. Control mechanisms are discussed, and some experimental and simulation results are reported.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.933-939
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• 2001

A Satellite shipping container must afford the satellite a relatively benign thermal, vibration, and particle environment that is oblivious to the extreme temperatures, sand, dust, vibrations and shocks that can accompany the transportation. In this study, we have designed a vibration isolation system of a spacecraft container that will be used to transport a satellite called KOMPSAT (KOrea Multi-Purpose SATellite) -2 from KARI (Korea Aerospace Research Institute) Taejon to its launch site. To identify the dynamic characteristics of the system, a 1/3-scaled mockup of the container was developed. A large electro-magnetic shaker (Max. 240 KN) was used to excite the mockup, and vibration signals from 20 points were collected for modal tests. Numerical simulations through CATIA 3D Modeling were performed to identify the behavior of isolation springs. The results showed that a simplified model predicts the behavior in a reasonable accuracy. Moreover, the model guides us how to design a full-scaled satellite-shipping container.